I'm very close to considering Sorcerer King my favorite fantasy 4X game ever. The only thing standing in the way is the longevity of replayability, but you're already addressing that. I'd also like to see some many-part quests eventually. However, it's really hitting the right notes with me. It may even beat out Endless Legend for me. No exaggeration...
I think it's because it plays just like the RPG/4X hybrid I've always wanted, where your adventuring leads to possible boons for your kingdom and party and the factions are interesting and tell a cool story. Going up against the big bad feels like the perfect culmination of all the adventures you have along the way. It IS a Fantasy Star Control in a lot of ways and yet better, too. No other game in this genre has captured the feeling of venturing out in to the world to find fame, fortune and revenge like SK does. Each time I've lost, I've been really eager to start another game. Most games in this genre compel me to take a little time off with them before doing so. I can count on one hand the amount of games that I'm this excited to begin again with...
Anyway, 5.2 is great. There are some niggling bugs and other issues, but the game is just so damn good. I'm *still* finding new things and the game remains challenging.
If you all can shore up the replayability concerns and execute the expanding minors well, this game will be your best yet. That's not hyperbole.
So, yeah, keep up the good work.